public class LinkedList {
    static class ListNode{
        private int val;
        private ListNode prev;
        private ListNode next;
        public ListNode(int val){
            this.val=val;
        }
    }
    public ListNode head;
    public ListNode last;
    //头插法
    public void addFirst(int data){
         ListNode node = new ListNode(data);
         if(head==null){
             head=node;
             last=node;
         }else{
             node.next=head;
             head.prev=node;
             head=node;
         }

    }
    //尾插法
    public void addLast(int data){

        ListNode node = new ListNode(data);
        if(head==null){
            head=node;
            last=node;
        }else{
            last.next=node;
            node.prev=last;
            last=node;
        }
    }
    private void checkIndex(int index)throws IndexOutOfException{
        if(index<0||index>size()){
            throw new IndexOutOfException("index不合法"+index);
        }
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        checkIndex(index);
        if(index==0){
            addFirst(data);
            return;
        }
        if(index==size()){
            addLast(data);
            return;
        }

    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur =head;
        while(cur!=null) {
            if(cur.val==key){
              if(cur==head){
                  head=head.next;
                  if(head!=null){
                      head.prev=null;
                  }else{
                      last=null;
                  }
              }else{
                  if(cur.next!=null){
                      cur.prev.next=cur.next;
                      cur.next.prev=cur.prev;
                  }else{
                      cur.prev.next=cur.next;
                      last=last.prev;
                  }

              }
              return;
            }else{
             cur=cur.next;
            }
        }


    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur =head;
        while(cur!=null) {
            if (cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    } else {
                        last = null;
                    }
                } else {
                    if (cur.next != null) {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    } else {
                        cur.prev.next = cur.next;
                        last = last.prev;
                    }

                }
            }
            cur=cur.next;
        }
    }
    //得到单链表的长度
    public int size(){
        int count = 0;
        ListNode cur =head;
        while(cur!=null){
            count++;
            cur=cur.next;
        }
        return count;
    }

    public void display(){
        ListNode cur =head;
        while(cur!=null){
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
    }

    public void clear(){
       ListNode cur = head;
       while(cur!=null){
            ListNode curNext = cur.next;
            cur.prev=null;
            cur.next=null;
            cur=curNext;
       }
       this.head=null;
       this.last=null;
    }
}
